Interaction of Genotype and Environnment in Expression of Phenotype: Do University Students Integrate Knowledge About Epigenetics
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Education Research Highlights in Mathematics, Science and Technology 2016 INTERACTION OF GENOTYPE AND ENVIRONNMENT IN EXPRESSION OF PHENOTYPE: DO UNIVERSITY STUDENTS INTEGRATE KNOWLEDGE ABOUT EPIGENETICS Boujemaa AGORRAM Cadi Ayyad University, Morocco Sabah SELMAOUI Cadi Ayyad University, Morocco Moncef ZAKI Sidi Mohamed Ben Abdellah University, Morocco Salaheddine KHZAMI Cadi Ayyad University, Morocco ABSTRACT: In recent decades, genetic issues play a large role in health and public policy and new knowledge in this field continues to have significant implications for individuals and society. In spite of this increased exposure to genetics, recent studies of the general public’s genetics knowledge show a relatively low understanding of genetics concepts. Epigenetics is a new paradigm in biology. Nevertheless, the notion of genetic determinism is still present in syllabuses and textbooks. The present research explores the university students’ conceptions related to the genetic determinism of behaviors and human performances and if they integrate recent knowledge in Epigenetics. The research method is a questionnaire elaborated by the Biohead-Citizen consortium. The findings revealed that these students were still reducing the biological identity to a genetic program. The set can also enhance the danger of hereditarian ideology that justifies the fatalism and racism. We concluded that the teaching of epigenetics becomes a scientific and citizen challenge. Key words: Genetic determinism, students, conceptions INTRODUCTION In the twentieth century, the nature-versus-nurture debate was one of the most important themes of genetics (Castera et al, 2008). Now, most scientists accept that both factors have a crucial role and that phenotypes result from the actions and interactions of both, which often change over time (Petronis, 2010). Most phenotypes show some degree of heritability, a finding that formed the basis for a series of molecular studies of genes and their DNA sequences (Nicol-Benoit et al, 2013). In parallel to such genetic strategies, thousands of studies have been carried out to identify environmental factors that contribute to phenotypes (Georgel, 2015). The new paradigm is not one of nature versus nurture, but of a complex and dynamic interaction between DNA sequence, epigenetic DNA modifications, environment, gene expression, and environmental factors that all combine to influence phenotype (Gibson, 2008; Kilpinen et Dermitzakis, 2012). Over the last years, several university programs introduced bit by bit epigenetics as part of the genetics (regulation of the expression of multiple genes, cell differentiation…). However, in most countries, university programs of Biology do not include the wealth of information gathered over the last 30 years of investigation of epigenetics. This article aims to explore if the students integrate the recent scientific knowledge about Epigenetics when they are asked about relationship between Genotype and environment in expression of phenotype. The article also tends to identify their conceptions related to the genetic determinism of behaviors and human performances. THEORETICAL BACKGROUND The Genotype-Phenotype Relationship The Genotype, carried by all living organisms, holds the critical instructions that are used and interpreted by the cellular machinery of the cells to produce the "outward, physical manifestation", or Phenotype of the organism. Thus, all the physical parts, the molecules, macromolecules, cells and other structures, are built and maintained by cells following the instructions given by the genotype. As these physical structures begin to act and interact with one another, they can produce larger and more complex phenomena such as metabolism, energy utilization, tissues, 39 Education Research Highlights in Mathematics, Science and Technology 2016 organs, reflexes and behavior; anything that is part of the observable structure, function or behavior of a living organism (Braun, 2015). The genotype of a cell is its genetic makeup while the phenotype encompasses its traits, such as morphology and function. Genotype and phenotype represent two separate cellular entities; while the former is the structure of the genome-the DNA sequence, the latter is the determination of the form, growth and interactions with the external world of the cell. It can be any observable property of the living organism. The establishment of a phenotype, given a certain genotype, depends on the protein makeup of the cell. The set of expressed proteins, a subset of the entire genome potential, and their concentrations, are determined by regulatory systems at many levels. Thus, the emerging phenotype depends on the spectrum of regulatory modes-temporal profiles of expressed genes. However, a snapshot of the molecular content of a cell and the structure of its underlying interactions do not capture the spectrum of regulatory profiles that define the relevant observables that determine the phenotype (Braun, 2015). The protein content of each isolated gene is by itself not such a relevant observable. Therefore, inquiring into the genotype-to-phenotype associations requires a shift in focus from structure to dynamics, from the molecular stuff of the cell to its temporal organization. The genotype-to-phenotype mapping is largely assumed to be deterministic in nature, accompanied by ‘noise’ by environmental influences and intracellular stochastic processes due to the small volume of the cell and the small number of molecules involved (Braun, 2015). Epigenetics Epigenetics has become a topic with implications across a diversity of biological disciplines, inspiring exciting theoretical and empirical work. The term dates back to the work of Waddington in the 1940s who was one of the earliest researchers to disavow a simple relationship between genotype and phenotype. Since that time, interpretations of the term have evolved, particularly as molecular-level mechanisms that modulate gene expression have been revealed. Still, even since Waddington, the term has been used to refer to the interactions of the genome with the internal and external environment in the production of phenotypes (Richards, 2012). Prior to the middle of the twentieth century, before DNA was given a special status in biology, the developmental biologist and evolutionist Waddington (1905-1975) emphasized that genetics and developmental biology were related, hypothesizing that patterns of gene expression, turning genes on and off, and not the genes themselves, define each cell type, thus linking genes and gene action to development. To denote the dynamic actions leading from the genotype to the phenotype, Waddington coined the term ‘epigenetics’ from the Greek word epigenesist, referring to embryology and genetics as “a gradual coming into being of newly formed organs and tissues out of an initially undifferentiated mass”. In this way, Waddington indicated that an epigenetic landscape underlies each developing organism, referring to the existence of a complex network in which genetic interactions, the feedback and “feedforward” relationships among DNA, proteins, and other internal and external biochemical compounds are highly intermingled. Riggs (1975) proposes a molecular model for the switching of gene activities, and also the heritability of gene activity or inactivity. This model was based on the enzymatic methylation of cytosine in DNA. The suggestion was that DNA methylation could have strong effects on gene expression, and changes in DNA methylation may therefore explain the switching on and off of genes during development, and that the pattern of methylation could be heritable, persisting through cell divisions (Barros & Offenbacher, 2009). Epigenetics, as the term suggests, can be seen as a major turn away from molecular biology’s Central Dogma, recognizing that there are epigenetic inheritance systems through which no sequence-dependent DNA variations can be transmitted in cell, tissue, and organismal lineages (Barros et Offenbacher, 2009). Models of Genotype-Phenotype Relationship The concept of phenotype, which corresponds to the observable attributes of an individual, was coined in opposition to the genotype, the inherited material transmitted by gametes. Since the early proposal that genotypes and phenotypes form two fundamentally different levels of biological abstraction, the challenge has been to understand how they articulate with each other, how genotypes map onto phenotypes. Linear Causal Model From a genetic change causing a variation in phenotype, it is often convenient to assimilate the corresponding gene as a causal determinant of a trait (Figure 1a). It is common to find headlines expressing these simplifications, 40 Education Research Highlights in Mathematics, Science and Technology 2016 trumpeting to wide audiences the discovery of the “aggressiveness” or “intelligence” gene. According to this model a variation at a given gene causes variation in a given phenotype (Waters, 2007). The genetic reductionist approach, which only explores a few genetic parameters among the variety of causal factors, is vain to fully address the broad question of what brings forth a particular biological structure or process in its entirety. Nevertheless, genetic reductionism can be perfectly appropriate for identifying genetic loci where a change causes a phenotypic difference (Orgogozo et al 2015). a - Linear causal b - Additive model c - Interactive model model Genotype Genotype Environment Genotype Environment Phenotype Phenotype